Denial of service via RDP ZGFX off-by-one
Published Aug 19, 2026 · Updated Aug 20, 2026
Heap-based buffer overflow in Wireshark 4.6.0 through 4.6.7 and 4.4.0 through 4.4.17 allows attackers to crash Wireshark via malformed RDP data. In tvbuff_rdp.c, zgfx_write_literal() checks whether outputCount equals 65535 instead of whether it has reached or exceeded outputSegment[65536], so a prior ZGFX match can raise the counter to 65536 and the next literal write overruns the heap buffer. Reachability is through passive packet analysis: a crafted packet on the wire or a malicious capture file can trigger a crash, and the published advisory bounds the confirmed impact to service interruption.
Summary
What happened
Heap-based buffer overflow in Wireshark 4.6.0 through 4.6.7 and 4.4.0 through 4.4.17 allows attackers to crash Wireshark via malformed RDP data. In tvbuff_rdp.c, zgfx_write_literal() checks whether outputCount equals 65535 instead of whether it has reached or exceeded outputSegment[65536], so a prior ZGFX match can raise the counter to 65536 and the next literal write overruns the heap buffer. Reachability is through passive packet analysis: a crafted packet on the wire or a malicious capture file can trigger a crash, and the published advisory bounds the confirmed impact to service interruption.
The record
- CVE
- CVE-2026-76888
- Published
- Aug 19, 2026
- Updated
- Aug 20, 2026
- Vendor
- Wireshark Foundation
- Product
- Wireshark
- Classifications
- CWE-122
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 19, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4.4.0 <4.4.18
- Affected versionversion=4.6.0 <4.6.8
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Wireshark issue 21396 proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo